Conventionally, in an electric motor, starting and ending leads of the coils of wire wound around armature core teeth are connected to the corresponding segments of a commutator by shortest possible distances. There are two major problems in manufacturing such armatures. First, since the winding process for the coils and the crimping or soldering process for connecting the coil wire to the tangs of the commutator are performed as separate processes, the very first starting end of the coil wires is required to be held to the first tang with a special jig such as a pair of jaws because a considerable tension is applied to the coil wire as it is being wound and the need for such a jig is detrimental to the efficiency of the manufacturing process. Further, the need to synchronize the motion of the jig to the initial indexing motion applied to the armature is also detrimental to the efficiency of the manufacturing process. Second, successively wound coils of wire tend to apply pressure to the leads of the previously wound coils of wire and care is needed to prevent damage to the coil wire as a result of this pressure from the subsequently wound coils. This could cause a serious problem depending on the sizes of the armature and the commutator and the distance between them.
To the end of eliminating the first problem, U.S. Pat. No. 3,191,269 discloses an anchoring method for securing the coil wire while winding the first coil in which a certain length of the starting end of the coil wire is passed through one of the core slots towards the commutator and is then hooked to the very first commutator tang. According to this method, since the starting end of the coil wire is thus anchored, the coil wire stays engaged to the commutator tangs until the first coil is fully wound and the coil wire can be permanently connected to the tangs by soldering or welding afterwards. This proposal eliminates the first problem mentioned above in securing coil leads while the first coil is being wound but this method involves a certain length of loose starting lead which needs to be trimmed. Furthermore, it is impossible to completely trim this loose end because the loose end is covered by the subsequently wound coils.
U.S. Pat. Nos. 3,506,864 and 3,448,311 propose methods of winding a motor armature in which the coil leads connected to commutator segments are made to extend obliquely along the circumferential direction. According to these proposals, the coil leads extend partly tangentially in relation with the rotary shaft and the second problem mentioned above is avoided because the coil leads are passed adjacent to the outer circumferential surface of the rotary shaft so as to involve a certain tangential component and get wrapped closely around the rotary shaft.
However, according to these proposals, since the armature is required to be indexed over a large angle after connecting the starting end of the coil wire to the very first tang of the commutator, some problems arise in keeping the starting end of the coil wire held onto the commutator tang. Therefore, substantial alteration must be made to the armature winding machine to implement these methods and the cost for this alteration may be too high to be acceptable.